Gefran Melt Pressure Sensors
Transducers and Transmitters
The high temperature melt pressure transducer is an electronic device that transforms a physical variable (pressure) into an electrical signal (current or voltage or in Can Open, IO-Link, HART), acquired by the various control, measurement and regulation devices.
GEFRAN melt sensors are pressure/temperature transducers and transmitters designed for use in environments that reach very high temperatures, capable of detecting average pressure up to 538 °C.
Based on two main construction technologies (with extensometric filling fluid technology or totally fluid free with silicon piezoresistive technology), Gefran high temperature pressure sensors are available in 4 different designs: rigid stem, flexible sheath, flexible with thermocouple and exposed capillary.
Their high immunity to electromagnetic interference allows these sensors to be installed in any operating environment.
The devices guarantee vast coverage of detectable pressures, from the minimum range with a scale of 0-17 bar up to a range of 0-3000 bar.
The available output signals are mV/V, 4-20mA, 0-10V, Gauge type, CANOpen, and IO-Link. Atex and PLd and SIL 2 versions complete the range for the various architectures and applications present on the plastics converting machinery market.
The Melt sensor is ideal for applications in the polymer production and processing industry.
Key Advantages of Use of Melt Probes
Use of melt probes is indispensable in extrusion processes as they contribute:
To the safety of the system when used to prevent an uncontrolled rise in machine pressure.
To improving the performance of production with their ability to keep flow-rate stable and optimal.
Melt sensors are normally used in pressure reading:
along the cylinder to check its performance during the development and design of the screw
in the filter changer to check its cleanliness
before and after the gear pump to keep the flow rate constant
in the head for closed-loop pressure control.
Application Sectors
Extrusion
Injection-blow Moulding
Hot Melt (Glue Dosing)
Polymer Production
Injection
Thermodynamic Concentrated Solar Power CSP Installations
Technology
Gefran uses one of the most widespread and proven existing measurement principles, the so-called "Wheatstone Bridge". There are a number of different technologies for making the sensitive element on the basis of this principle.
Fully Fluid-Free Piezoresistive Technology
The innovative IMPACT sensors (series I) are pressure transmitters, without transmission fluid, in which the medium pressure is transferred directly to the silicon sensing element through a thick membrane. The transduction of the physical stress is entrusted to a Wheatstone bridge made by means of 4 piezoresistors.
The IMPACT series, Gefran's proprietary technology, is characterized by:
Remarkable robustness (up to 15 times that of a conventional sensor)
Notable response speed
Extreme ease of installation thanks to the modularity of the sensor
High safety standards (compliance with Machine Directives and RoHS)
Thick Film on Steel with Filling Fluid Technology
The operating principle is based on the hydraulic transmission of pressure by means of filling liquids with a low compressibility coefficient: sodium-potassium NaK mixture (K series), FDA approved diathermic oil (W series) and mercury (M series, available only in cases permitted by European Directive 2011/65/EU - RoHS II). The entire structure is therefore designed to transfer the pressure exerted by the medium on the contact diaphragm to the transduction part, i.e. the measuring diaphragm on which the strain gauge is located, taking care to keep it away from the heat source. The strain gauge then translates the pressure into an electrical signal.
Using the "screen printing process" technique, the insulating layers (dielectric), the conductive layer (cermet) and the resistive layer are deposited on the steel membrane to create the "Wheatstone bridge".
Self-Compensation
Through the SP option, internal self-compensation, K/W/M series transmitters cancel the effect of pressure signal variation caused by melt temperature variation.
In this way, the reading error caused by heating of the filling fluid (typical in filled sensors) is reduced to a minimum.
In melt pressure probes with IMPACT technology, digital electronics can automatically compensate drift due to the thermal effect.
Power-Flo Technologies is proud to partner with Gefran and their high-temperature melt pressure sensors provide reliable pressure and temperature measurement for demanding polymer production and processing applications. With multiple construction technologies, pressure ranges, output signals, and configurations, these sensors offer the flexibility needed for a wide range of extrusion, injection, and hot melt applications. Advanced features such as fully fluid-free technology and self-compensation help support accurate, responsive measurement even in high-temperature environments. By helping monitor and control pressure throughout the production process, Gefran melt sensors contribute to improved system safety, process stability, and overall production performance.